The present invention relates to improved method and apparatus for continual treatment of textile sheet material by application of microwaves, and more particularly relates to improvement in continual treatment of a textile sheet material such as a woven cloth within an atmosphere replete with saturated or overheated steam under emanation of microwaves for uniform treatment effect over the entire length and thickness.
Fixation and development of dyes on a textile sheet material such as a woven cloth has long been carried out by placing the textile sheet material in an atmosphere impregnated with steam.
As a substitute for such a steam process, it was already proposed to subject a textile sheet material to emanation of microwaves in wet state. Here, the term "microwaves" refers to electro-magnetic waves having frequencies in a range from 300 to 30,000 MHz.
Use of microwaves has a wide variety of advantages in particular when they are used for treatments of a textile sheet material in wet state. First, they permeate into and heat the textile sheet material very quickly. Secondly, since their heat generation is dependent upon dielectric loss, they can be selectively absorbed in an object with large dielectric loss and, heat only necessary sections of the object. There is no heating of unnecessary sections of the object, thereby well avoiding extravagance of thermal energy. Thirdly, the object exposed to microwaves generate heat by itself which naturally raises the temperature of the ambient atmosphere. As a consequence, the amount of the thermal energy otherwise needed for heating the ambient atmosphere can be greatly reduced. Fourthly, since microwaves cause almost simultaneous temperature rise at different sections of the object exposed to them, regional variation in temperature within the object can be significantly minimized and this leads to ideal and uniform heating of the object. Finally, adjustment of the output voltage for microwave generation enables simple, easy and swift control of the heating condition in accordance with demands in actual treatment of textile sheet materials.
Emanation of microwaves onto a textile sheet is said to cause ionic conduction and dipole rotation of the fibers composing the material and water and/or agents contained in the material. This is believed to result in the swift and uniform heating of the textile sheet material.
Based on recognition of these advantages, various systems have been proposed in the field in order to utilize microwaves in practical treatments of textile sheet materials, but almost all of them were barely feasible in industrial scale.
One reason for such difficulty is the manner of microwave emanation. Various emanators are in general used to this end, and they are roughly classified into three major types, i.e. an emanator with a densely hairpin curved wave guide, and an open-type emanator.
In the case of the emanator equipped with the wave guide, the wave length of the emanated microwave wields a great influence upon the heating effect and, consequently, the textile sheet material is liable to undergo uneven heating to be caused by possible variation in the wave length. Stable control of the wave length is highly difficult in practice. As a result, the emanators of this type are quite unsuited for treatments of wet textile sheet materials which usually require high uniform heating effect and are susceptible to damages caused by fluctuating heating effect.
In the case of the open-type emanator having a metallic hexadral emanation chamber, it is strongly required to employ any special expedients to equalize the intensity of the magnetic field around the material placed in the emanation chamber. Otherwise, the emanators of this type do not operate satisfactorily in industrial scale although they may operate well in laboratory tests.
Another fact causing the difficulty in practical use of microwaves in fusion of fibers composing a textile sheet material. Such fusion is caused by microwaves themselves. This gives a serious problem in particular when the textile sheet materials is composed of thermoplastic synthetic fibers such as acrylic fibers. Such fusion of fibers is caused by presence of water and high boiling point agents in the textile sheet material after finishing and souring. For example, when a textile sheet material is made of acrylic fibers, swelling of the fibers starts at a temperature very close to 100.degree. C. and, regardless of the dielectric constant, this swelling causes corresponding dipole rotation in the construction of the fibers. This dipole rotation results in abrupt evacuation of water and puts the fiber in arid state. Consequently, the temperature of the fiber rises quickly and such escalated temperature initiates fusion of the fibers composing the textile sheet material.
The other fact making practical use of microwaves difficult is the control of the above-described evacuation of water contained in the fibers. To this end, it is proposed to clamp a textile sheet material between a pair of running conveyer belts or place a textile sheet material on a running wet sheet during transportation through the microwave emanation zone. In either cases, there is high rate of danger that any contaminations on the belts or the sheets may be transferred to the textile sheet material during the treatment and this naturally causes serious degradation of the commercial value of the end product.
In order to remove such disadvantages inherent to the conventional textile treatment with microwaves, the inventor of the present invention has already proposed in U.S. Pat. No. 4,274,209 and in EPC Patent Application No. 79850116.9 to place a textile sheet material in the form of a roll within a confined chamber replete with saturated or overheated steam and rotate the roll under concurrent emanation of microwaves.
This proposed system well removed most disadvantages of the conventional textile treatment with microwaves. However, since the textile sheet material in this system is exposed to steam and microwaves in a roll form, there is a significant difference in treatment effect between the section of the textile sheet material close to the core of the roll and the section close to the periphery of the roll. As a consequence, one cannot expect uniform treatment effect over the entire length and textile sheet material.
In order to remove this advantage, a more dynamic system has also been proposed by the inventor of the present invention. In accordance with the dynamic system, a pair of rolls of a textile material are placed within a confined chamber replete with saturated or overheated steam, and the textile sheet material is continually transferred from one roll to another and vice versa under concurrent emanation of microwaves.
This improved system well solve the uniformity problem. However, since the textile sheet material has to kept, even provisionally, within the confined chamber during the treatment, this system is applicable to the so-called batch system process only. In other words, this system is quite unsuited to any continuous textile process in which a textile sheet material has to be continually transported from station to station.